Conversions of low molecular weight hydrocarbons to higher molecular weight hydrocarbons using a metal compound-containing catalyst

ABSTRACT

Disclosed is a catalytic process for the production of higher molecular weight hydrocarbons from lower molecular weight hydrocarbons. More particularly, disclosed is a catalytic process for the conversion of methane to C 2  + hydrocarbons, particularly hydrocarbons rich in ethylene or benzene, or both. The process utilizes a metal-containing catalyst, high reaction temperature of greater than 1000° C., and a high gas hourly space velocity of greater than 3200 hr -1 .

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of Ser. No. 547,699, filedOct. 31, 1983, now U.S. Pat. No. 4,599,474, the entire disclosure ofwhich is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a catalytic process for the productionof higher molecular weight hydrocarbons from lower molecular weighthydrocarbons. In particular the process of the present inventionutilizes a metal-compound containing catalyst under C₂ + hydrocarbonsynthesis conditions such that at least 15 mole percent cf the lowermolecular weight hydrocarbons in the feed gas are converted to highermolecular weight hydrocarbons, said conditions including a temperatureof greater than 1000° C. and a gas hourly space velocity of greater than3200 hr⁻¹. More particularly, the present invention relates to theconversion of methane using a Group IA metal compound containingcatalyst.

BACKGROUND OF THE INVENTION AND PRIOR ART

It is the business of many refineries and chemical plants to obtain,process and upgrade relatively low value hydrocarbons to more valuablefeeds, or chemical raw materials. For example, methane, the simplest ofthe saturated hydrocarbons, is often available in rather largequantities either as an undesirable by product in admixture with othermore valuable higher molecular weight hydrocarbons, or as a component ofan off gas from a process unit, or units. Though methane is useful insome chemical reactions, e.g., as a reactant in the commercialproduction of methanol and formaldehyde, it is not as useful a chemicalraw material as most of the higher molecular weight hydrocarbons. Forthis reason process streams which contain methane are usually burned asfuel.

Methane is also the principal component of natural gas, which iscomposed of an admixture of normally gaseous hydrocarbons ranging C₄ andlighter and consists principally of methane admixed with ethane,propane, butane and other saturated, and some unsaturated hydrocarbons.Natural gas is produced in considerable quantities in oil and gasfields, often at remote locations and in difficult terrains, e.g.,offshore sites, arctic sites, swamps, deserts and the like. Under suchcircumstances the natural gas is often flared while the oil isrecovered, or the gas is shut in, if the field is too remote for the gasto be recovered on a commercial basis. The construction of pipelines tocarry the gas is often not economical, due particularly to the costs ofconnecting numerous well sites with a main line. Transport of naturalgas under such circumstances is also uneconomical because methane atatmospheric pressure boils at -258° F. and transportation economicsdictate that the gas be liquefiable at substantially atmosphericpressures to reduce its volume. Even though natural gas containscomponents higher boiling than methane, and such mixtures can beliquefied at somewhat higher temperatures than pure methane, thetemperatures required for condensation of the admixture is nonethelesstoo low for natural gas to be liquefied and shipped economically. Underthese circumstances the natural gas, or methane, is not even ofsufficient value for use as fuel, and it is wasted.

The thought of utilizing methane from these sources, particularlyavoiding the tremendous and absolute waste of a natural resource in thismanner, has challenged many minds; but has produced few solutions. It ishighly desirable to convert methane to hydrocarbons of higher molecularweight (hereinafter, C₂ +) than methane, particularly admixtures of C₂ +hydrocarbon products which can be economically liquefied at remotesites; especially admixtures of C₂ + hydrocarbons rich in ethylene orbenzene, or both. Ethylene and benzene are known to be particularlyvaluable chemical raw materials for use in the petroleum, petrochemical,pharmaceutical, plastics and heavy chemicals industries. Ethylene isthus useful for the production of ethyl and ethylene compounds includingethyl alcohol, ethyl ethers, ethylbenzene, styrene, polyethylbenzenesethylene oxide, ethylene dichloride, ethylene dibromide, acetic acid,oligomers and polymers and the like. Benzene is useful in the productionof ethylbenzene, styrene, and numerous other alkyl aromatics which aresuitable as chemical and pharmaceutical intermediates, or suitable inthemselves as end products, e.g., as solvents or high octane gasolinecomponents.

It has been long known that methane, and natural gas could bepyrolytically converted to C₂ + hydrocarbons. For example, methane ornatural gas passed through a porcelain tube at moderate red heat willproduce ethylene and its more condensed homologues such as propylene, aswell as small amounts of acetylene and ethane. Methane and natural gashave also been pyrolytically converted to benzene, the benzene usuallyappearing in measurable quantities at temperatures above about 1650° F.(899° C.), and perhaps in quantities as high as 6-10 wt. % at 2200° F.to 2375° F., (1204° to 1302° C.) or higher. Acetylene and benzene inadmixture with other hydrocarbons, have been produced from methane andnatural gas in arc processes, cracking processes, or partial combustionprocesses at temperatures ranging above about 2775° F. (1524° C.). Heatfor such reactions has been supplied from various sources includingelectrically heated tubes, electric resistance elements, and spark orarc electric discharges. These processes characteristically requireconsiderable heat energy which, most often, is obtained from combustionof the by-product gases. The extreme temperatures coupled with the lowyields of higher molecular weight hydrocarbons have made the operationof such processes uneconomical.

High temperature, noncatalytic, thermal pyrolysis processes involvingthe conversion of methane in the presence of ethane and otherhydrocarbons are well known in the art. Representative articles include:Roczniki Chemi, An. Soc. Chim. Polonorum, 51, 1183 (1977), "TheInfluence of Ethane on Thermal Decomposition of Methane Studied By TheRadio Chromatographic Pulse Technique"; J. Soc. Chem. Ind. (Trans. andComm.) 1939,58, 323-7; and J. Chin. Chem. Soc. (Taipei) 1983, 30(3),179-83.

Addition of hydrogen to pyrolysis reaction mixtures is well known, seefor example, pp. 84-85 in "Pyrolysis Theory and Industrial Practice", L.F. Albright, B. L. Crynes and W. H. Corcoran (Ed.), Academic Press(1983).

Partial oxidation processes of converting methane to C₂ + hydrocarbonsare well known. In these processes, hydrogen must be removed either aswater, molecular hydrogen or other hydrogen-containing species.Likewise, any other polymerization mechanism wherein methane isconverted to C₂ + hydrocarbon products requires a tremendous amount ofenergy, most often supplied as heat, to provide the driving force forthe reactions. In the past the molecular hydrogen liberated by thereaction has often been separated and burned to provide the necessaryprocess heat. This route has proven an abomination to the production ofC₂ + hydrocarbons, but alternate reaction pathways have appeared littlebetter, if any, for these have resulted in the production of largequantities of the higher, less useful hydrogen deficient polymericmaterials such as coke, and highly oxidized products such as carbondioxide and water.

Typical of low temperature prior art processes are those disclosed inU.S. Pat. Nos. 4,239,658, 4,205,194 and 4.172,180 which use aregenerable catalyst-reagent. U.S. Pat. No. 4,239,658, for example,teaches a process for the conversion of methane to higher molecularweight hydrocarbons. In the process, a three component catalyst-reagentis utilized which comprises a mixture of various metals and metaloxides, particularly a Group VIII noble metal, nickel or a Group VI-Bnoble metal, a Group VI-B metal oxide and a Group II-A metal. The patentteaches process temperatures from about 1150° to 1600° F. (621° to 871°C.), preferably 1250° F. to about 1350° F. (677° to 732° C.).

It has also been reported in Science 153, 1393, (1966), "HighTemperature Synthesis of Aromatic Hydrocarbons From Methane", thataromatic hydrocarbons can be prepared from methane by contact withsilica at 1000° C. (1832° F.). The yield of hydrocarbons was in therange of 4.8 to 7.2 percent based on the methane used in a single passat a space velocity of 1224 hr⁻¹.

In the J. Chinese Chem. Soc., Volume 29, pages 263-273 (1981), it isreported that methane can be converted to C₂ + hydrocarbons attemperatures of 800° to 130° C. and space velocities of 3100 hr⁻¹ orless using a metal oxide catalyst. However, the total conversion ofmethane, at best, is 7.5 mole percent using a thorium oxide catalyst.

Franz Fischer, reports in an article entitled: "The Synthesis of BenzolHydrocarbons From Methane At Ordinary Pressure and Without Catalyst"(Brennstoff-Chemie, Vol. 9, pp. 309-316, 1928) that methane is convertedto benzol hydrocarbons by passing methane through a hot tube. Incarrying out this work Fischer tested many substances for catalyticactivity at temperatures ranging from 650° to 1150° C. and at high flowrates and concluded that the substances tested were not catalytic andnot necessary. Among the substances tested were elemental iron, copper,tungsten, molybdenum, tin and carbon; and the compounds potassiumhydroxide and silica gel.

SUMMARY OF THE INVENTION

A process for the production of higher molecular weight hydrocarbonsfrom lower molecular hydrocarbons comprising the steps of:

(a) introducing into a reaction zone a lower molecular weighthydrocarbon-containing gas and contacting said gas in said zone with ametal compound-containing catalyst under C₂ + hydrocarbon synthesisconditions such that at least 15 mole percent of the lower molecularweight hydrocarbons in said gas are converted to higher molecular weighthydrocarbons, said conditions including a temperature of greater than1000° C. and a gas hourly space velocity of greater than 3200 hr⁻¹ ;

(b) withdrawing from said reaction zone a higher molecular weighthydrocarbon-containing stream.

The process of the present invention affords high conversions of 19 molepercent or more of the lower molecular weight hydrocarbons with highselectivity, that is, 80 mole percent or more of the reaction productscomprise higher molecular weight hydrocarbons.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

It is a primary object of the present invention to provide an improvedprocess for the conversion of low molecular weight hydrocarbons tohigher molecular weight hydrocarbons with a high conversion of the lowermolecular hydrocarbons and high selectivity in the conversion to highermolecular weight hydrocarbons.

It is an essential feature and critical to obtaining the above objectsthat the process of the present invention is carried out under criticalreaction conditions. These critical conditions include the use of ametal compound-containing catalyst, a temperature of at least 1000° C.and a gas hourly space velocity of at least 3200 hr⁻¹.

It has been surprisingly found that by using the high contacttemperatures of the present invention coupled with the high spacevelocity, the metal compound-containing catalyst used in the presentinvention do not rapidly foul and the yield of less valuable coke is lowwhile the yield of higher molecular weight hydrocarbons is high.

As used in the present invention the word "metal" refers to all thoseelements of the periodic table which are not non-metals. "Non-metals"for the purpose of the present invention refers to those elements havingatomic numbers 1, 2, 5 through 10, 14 through 18, 33 through 36, 52through 54, 85 and 86.

As used in the present invention the phrase "lower molecular weighthydrocarbons" means hydrocarbons containing at least one or more carbonatoms, i.e., methane, ethane, propane, etc. Also as used in the presentinvention, the phrase "higher molecular weight hydrocarbons" meanshydrocarbons containing two or more carbon atoms and at least one carbonatom more than the lower molecular weight feedstock.

As used herein the phrase "C₂ + hydrocarbon synthesis conditions" refersto the selection of feedstock, reaction temperature, space velocity andcatalyst described hereafter such that higher molecular weighthydrocarbons are produced in the process with yields as describedhereafter. Other process parameters necessary to maintain C₂ +hydrocarbon synthesis conditions, such as the selection of particulartypes of reaction vessels, etc., is readily determined by any personskilled in the art.

The word "catalyst" is used in the present invention to mean a substancewhich strongly affects the rate of a chemical reaction but which itselfundergoes no chemical change although it may be altered physically bychemically absorbed molecules of the reactants and reaction products.

As used in the present invention the phrase "continuous catalyticprocess" means a process in which feedstock and products aresimultaneously fed to and removed from a reaction zone containing acatalyst.

As used in the present invention the words "light aromatics" refers tosingle ring aromatic hydrocarbons, for example, benzene, toluene,xylenes, and so forth.

The Feedstock and Products

Generally, the feedstock lower molecular weight hydrocarbon of thepresent invention will comprise methane or natural gas containing C₁ toC₄ hydrocarbons. The product higher molecular weight hydrocarbons willcomprise C₂ + hydrocarbons, particularly mixtures of C₂ + hydrocarbonswhich can be economically liquefied. Preferably, the higher molecularweight hydrocarbon product streams will be rich in ethylene or aromaticssuch as benzene, or both.

The process of the present invention affords high conversions of thelower molecular weight hydrocarbons with high selectivity to highermolecular weight hydrocarbons. More particularly, as measured by thedisappearance of the lower molecular weight hydrocarbons, the process ofthe present invention affords conversions of 19 mole percent or more ofthe lower molecular weight hydrocarbons, and preferably, the conversionsare greater than 25 mole percent and more preferably greater than 40mole percent. The carbon-containing reaction products comprise 80 molepercent or more higher molecular weight hydrocarbons, preferably,greater than 90 mole percent. Based on the feed, at least 15 molepercent, and preferably at least 20 mole percent, and more preferably atleast 40 mole percent of the lower molecular weight hydrocarbons areconverted to higher molecular weight hydrocarbons which is referred toherein as selectivity.

Process Conditions

It is critical to the process of the present invention that a hightemperature greater than 1000° C. is maintained in the reaction zonealong with a high gas hourly space velocity of greater than 3200 hr⁻¹.Preferably, the temperature will be greater than 1100° C. with a spacevelocity greater than 6000 hr⁻¹. Still more preferably the temperatureis greater than 1150° C. with a space velocity greater than 9000 hr⁻¹.

Generally, the temperature will be in the range of 1001° to 1300° C.while the gas hourly space velocity is in the range 3200 to 360,000hr⁻¹. Preferably, the temperature is in the range 1100° to 1200° C. witha gas hourly space velocity of 6,000 to 36,000 hr⁻¹. More preferably thetemperature is in the range 1140° to 1175° C. with a gas hourly spacevelocity in the range of 9,000 to 18,000 hr⁻¹. Generally, hightemperatures are used with high space velocities and low temperaturesare used with low space velocities.

The process can be operated at sub-atmospheric, atmospheric, or supraatmospheric pressure to react and form the higher molecular weight C₂ +hydrocarbons. It is preferred to operate at or near atmospheric pressureor within about 15 psi of atmospheric pressure.

The Catalysts

The lower molecular weight hydrocarbons are introduced into a reactionzone containing a suitable metal compound-containing catalyst.

A wide range of metal compound-containing catalysts and catalystsupports may be used in the present invention. Many commerciallyavailable catalysts which have been used in different processes aresuitable for use in the process of the present invention. The word"catalyst" is used in the present invention to mean a substance whichstrongly affects the rate of a chemical reaction but which itselfundergoes no chemical change although it may be altered physically bychemically absorbed molecules of the reactants and reaction products. Itis also understood that the catalyst of the present invention may beformed in situ. For example, in the present invention when an oxide,nitride, or carbide metal catalyst is initially charged to the reactor,the oxide and nitride may be converted in situ to the carbide which thenfunctions as the catalytic species.

Metal compound-containing catalysts for use in the present inventionwill provide conversion of the lower molecular weight hydrocarbons of atleast 19% and will maintain this conversion for at least 3 hours underthe temperature and space velocity conditions previously discussed.Preferred catalysts of the present invention will provide conversions of30% or more of the lower molecular weight feed and remain active for 3hours or more.

Representative metal compound-containing catalysts are refractorymaterials and include the compounds of the Group I-A, II-A, III-A, IV-Bor actinide series metals. Representative compounds include the carbide,nitride, boride or oxide of a Group I-A, II-A, III-A, IV-B or actinideseries metal, used alone or in combination.

The catalyst must be thermally stable under the operating condition inthe reaction zones and are preferably particulate in form. The carbidesof the Groups I-A, II-A, III-A, IV-B and actinide series metals areparticularly preferred because it is believed that the carbide metalcompound-containing catalyst are the most stable under the severereaction conditions of the present invention. Preferably, the catalystcan also be regenerated by the periodic burning-off of any undesirabledeposits such as coke. The regeneration of catalyst by the burning offcoke is well known in the catalyst and petroleum processing art.

Representative Group I-A metal compound-containing catalyst include thecarbide, nitride, boride, oxide of lithium, sodium, potassium, rubidium,and cesium. Most preferred among the Group I-A metals is lithium.

Representative Group II-A metal compound-containing catalysts includethe carbide, nitride, boride, or oxide of beryllium, magnesium, calcium,strontium, barium, and radium. Most preferred among the Group II-Ametals is calcium.

Representative Group III-A metal compound-containing catalysts includethe carbide, nitride, boride, or oxide of aluminum, scandium, yttrium,lanthanum, and actinium. Most preferred among the Group III-A metals isaluminum.

Representative Group IV-B metal compound-containing catalysts includethe carbide, nitride, boride, or oxide of titanium, zirconium, andhafnium. Most preferred among the Group IV-B metals is zirconium.

Representative actinide series metal compound-containing catalystsinclude the carbide, nitride, boride, or oxide of thorium and uranium.Most preferred among the actinide series metals is thorium.

Catalysts useful in the present invention may be used with and withoutcatalyst supports. However, it is generally preferred to use a catalystsupport such as the well known aluminas.

The catalysts useful in the present invention may have a wide range ofsurface areas as measured by the BET method using krypton [Jour. Am.Chem. Soc., vol. 60, pp. 309 (1938)]. Low surface areas are preferred.Generally, the catalyst will have a surface area in the range 0.1 to 10m² /gram, preferably in the range 0.2 to 2.0 m² /gram.

The reaction-zone catalyst system can be either of the fixed bed type orfluid bed type and the lower molecular weight hydrocarbons can beintroduced into the top or bottom of the reaction zone with the productstream removed from either the top or bottom. Preferably, a fixed bedcatalyst system is used and the feed stream is introduced into the topof the reaction zone and product is withdrawn from the bottom.

A particularly preferred catalyst for use in the present invention isthorium oxide on alumina.

The advantages of the present invention will be readily apparent from aconsideration of the following examples.

EXAMPLES

The examples illustrating the invention were carried out as follows:

The apparatus comprises a vertical reactor tube made of high purityalumina of 3/8" O.D. and 1/4" I.D. This tube is 24" long, the central12" of which is surrounded by a high temperature electric furnace(Marshall Model 1134). The heated section of the tube is packed with thetest catalyst. A small piece of close fitting alumina honeycomb, ormonolith, at the bottom of the bed supports the catalyst. An "O"-ringsealed closure at the top of the reactor tube connects it to a gas flowsystem, which permits either argon or methane to be passed into thereactor at a measured rate. Gas flows into the reactor are measured withpre-calibrated flowmeters. Gas exiting from the reactor is first passedthrough a trap packed with dry stainless steel "saddles" (distillationcolumn packing), then through a tube fitted with a rubber septum. Gassamples are taken through the septum with a syringe. Off gas exits thesystem through a "U"-tube partially filled with oil. Bubbles passingthrough the oil provide a visual indicator of the gas flow.

In operation, the central section of the reactor tube is packed with thecatalyst to be tested. The catalyst particles range in size from 8 meshto 12 mesh. About 10 cm³ of catalyst is charged to the reactor. Thereactor is then placed in the cold furnace, and the necessary input andoutput connections are made. A slow flow of about 15 to 20 ml/min. ofargon is continuously passed through the reactor, which is then broughtto the desired temperature over a period of about 150 min. Temperaturesreported in Table I are measured by a thermocouple mounted in thefurnace wall. Calibration curves, previously developed from athermocouple in the catalyst bed and compared to the furnace wallthermocouple, are used to determine the reaction temperatures reportedin Table I.

Once the reactor tube is at the desired temperature, argon flow isstopped and methane flow is started at the predetermined flow rate.Space velocities are calculated on the basis of the temperature,pressure, methane flow rate into the reactor and on the catalyst beddimensions. On each run, the reaction is allowed to level out for 15 to20 minutes before the first analytic sample is withdrawn through theseptum. Two samples are taken each time, using one ml gas-tightsyringes. Aliquots of these samples (0.25 ml) are separately injectedinto a gas chromatograph packed with Poropak Q. Analysis is made forhydrogen, methane, and light hydrocarbons having less than 5 atoms ofcarbon. Other aliquots of the same samples are injected into another gaschromatograph column packed with Bentone 1200. This analysis is made foraromatics, that is, benzene, toluene, and the xylenes. Those aromaticcompounds having more than eight carbon atoms are calculated as heavyhydrocarbons in this application.

Calculation of the yield and conversion values of Table I from the gasanalysis data only is as follows: First, the reaction is assumed to begiven by the general expression:

    CH.sub.4 →βC+γ"CH"+(2γ+1.5γ)H.sub.2

wherein "CH" represents the aromatics, C is coke plus higherhydrocarbons called tar/coke in Table I and β and γ are the number ofmoles of tar/coke and aromatics, respectively. Then, for one mole ofmethane fed to the reaction zone, α is the fraction that reactsaccording to the above equation and ##EQU1## wherein X_(CH).sbsb.4 isthe mole fraction of methane in the product gas stream. Finally, aniterative procedure is used to calculate β and γ based on the gasanalysis results.

Table I below gives the details of runs made in accordance with theabove description. The table gives the catalyst composition, the spacevelocity, temperature, and results of runs made on the conversion ofmethane to C₂ + hydrocarbons.

The apparatus and procedures used for obtaining the data in Table II wassubstantially the same as described above for Table I with the followingexceptions:

(1) A large diameter reactor tube (3/4" O.D.×1/2" I.D.) was used. Acentral thermowell was inserted in the reactor. The temperature of thecatalyst bed was measured at its midpoint, using aplatinum/platinum--10% rhodium thermocouple.

(2) The measurement of coke for data in Table II was carried out asfollows: Upon completion of a run to determine catalyst activity andselectivity, the feed was replaced by argon. Air was then added to theargon flow to an extent of 20% by volume. In the meantime, the trappingand sampling system at the reactor exit had been replaced by a COconverter and Ascarite traps to permit estimation of CO₂ formed byreaction of oxygen in the air/argon mixture with coke on the catalyst.Dilute air was used until the temperature maximum, produced by theexothermic coke/oxygen reaction, was past. Then the argon flow wasterminated, and 100% air was used at a flow rate equal to the feed flowto assure similar mass transport conditions. By these means, completecombustion of the coke on catalyst was obtained. Weighing the Ascariteabsorption tube before and after use afforded the weight of CO₂absorbed, from which the carbon content of the catalyst was readilycalculated. Appropriate tests were performed to determine that the COconverter was functioning, and that carbon combustion was complete;

(3) In the calculation of aromatics, heavy hydrocarbons, and coke forthe data in Table II, it was assumed that the carbon atoms fromconverted methane, and the carbon atoms from converted ethane, wereuniformly distributed among all the products. Thus, the proportion ofcarbon atoms in benzene that resulted from methane conversion was thecarbon atoms in total product benzene times the fraction ##EQU2##Calculation of moles or weight of benzene formed was then straightforward, from the stoichiometric relationships. Similarly calculationswere made for the other aromatic compounds and for coke. Finally, heavyhydrocarbon was calculated as the difference: carbon atoms fromconverted methane minus (carbon atoms in the light aromatics fromconverted methane plus carbon atoms in coke from converted methane).This difference was multiplied by 13.02 to obtain the weight of heavyhydrocarbon. Assuming a molecular weight of 13.02 corresponds to anassumption that the heavy hydrocarbons have a molecular formula of(CH)x. This is correct to within a few percent. Gas chromatographicanalysis of the heavy hydrocarbon collected in the traps showed thatabout 95% of the heavy hydrocarbon was useful product;

(4) In Table II, the % yield was calculated as follows: ##EQU3## Usefulproducts include (1) the aromatics (benzene toluene and the xylenes) and(2) the heavy hydrocarbons (polynuclear aromatic hydrocarbons containing4 and fewer fused rings).

It was assumed that the two to four carbon hydrocarbons formed asproducts were being recycled as feed to the process. The 5% ethane inthe feed used in the experiments recorded in Table II simulated thissituation. Thus the 5% ethane in the feed essentially corresponds to thetwo to four carbon hydrocarbons content of the process feed at steadystate operation in a reactor in which these products are recycled to thefeed.

                  TABLE I                                                         ______________________________________                                                             Results                                                                 Conv. Fraction of carbon                                                      mole  converted, appearing as                                  Reaction Conditions                                                                            % of    Light                                                Run  Cata-   Temp.   Sv    CH.sub.4                                                                            Hydro- Aro-  Tar/                            No.  lyst    °C.                                                                            hr.sup.-1                                                                           fed   carbons                                                                              matics                                                                              Coke                            ______________________________________                                        1    A       1130     3600 19    0.30   0.70  0                               2    B       1150     9000 24    0.38   0.47  0.15                            3    C       1190    18000 21    0.48   0.45  0.07                            4    D       1170    12000 24    0.36   0.45  0.19                            5    E       1170     9000 43    0.19   0.28  0.53                            6    E       1190    18000 27    0.34   0.42  0.76                            7    F       1170    18000 22    0.38   0.52  0.10                            8    G       1170    18000 35    0.19   0.22  0.59                            9    H       1130     3600 42    0.13   0.29  0.58                            10   I       1150     3600 32    0.23   0.36  0.41                            11   J       1190    18000 22    0.40   0.43  0.17                            12   H       1130     3100 55    0.15   0.07  0.77                            ______________________________________                                    

                                      TABLE II                                    __________________________________________________________________________                    Conv.   Results                                                               mole    Fraction of carbon                                                    %       converted, appearing as                               Reaction Conditions                                                                           of            Heavy                                           Run     Temp.                                                                             Sv  CH.sub.4      Hydro-                                          No.                                                                              Catalyst                                                                           °C.                                                                        hr.sup.-1                                                                         fed Yield                                                                             Aromatics                                                                           carbons                                                                           Coke                                        __________________________________________________________________________    13 D     975                                                                              12000                                                                             05  67  0.0   0.87                                                                              0.07                                        14 D    1170                                                                               3174                                                                             76   0  0.0   0.0 1.00                                        15 K    1100                                                                              12000                                                                             25  53  0.22  0.49                                                                              0.29                                        16 L     975                                                                              12000                                                                             04  69  0.18  0.70                                                                              0.12                                        17 L    1179                                                                               3174                                                                             73  13  0.02  0.15                                                                              0.83                                        18 L    1100                                                                              12000                                                                             24  58  0.21  0.54                                                                              0.25                                        19 A     976                                                                              12000                                                                             01  72  0.42  0.50                                                                              0.09                                        20 A    1140                                                                               3100                                                                             60  17  0.04  0.18                                                                              0.79                                        21 A    1100                                                                              12000                                                                             24  66  0.21  0.63                                                                              0.16                                        22 N     975                                                                              12000                                                                             01  65  0.40  0.42                                                                              0.18                                        23 N    1133                                                                               3100                                                                             53  14  0.05  0.18                                                                              0.79                                        24 N    1097                                                                              12000                                                                             22  65  0.28  0.54                                                                              0.18                                         25*                                                                             O    1070                                                                              12000                                                                             23  64  0.14  0.69                                                                              0.17                                        __________________________________________________________________________     *The feed in this case was 7.5% H.sub.2 + 5% C.sub.2 H.sub.6, balance         CH.sub.4                                                                 

Catalysts Used in Tables I & II

In the following catalyst descriptions a "/" is used to indicate thatthe compound following is a support.

A. Al₂ O₃ : White fused refractory alumina, purchased from CarborundumCompany.

B. ThO₂ /Al₂ O₃ : A saturated solution of Th(NO₃)₄ ·4H₂ O in dimethylformamide was prepared. Forty grams of White fused refractory alumina(Carborundum) in a stainless steel basket were dipped in the abovesaturated solution of thorium nitrate, and the solvent evaporated in avacuum oven. After several dippings and dryings the catalyst weight hadincreased to 43.03 gm. This material was then fired at 1000° F. for 10hrs. in air, and used in the reactor.

ThO₂ -Al₂ O₃ -Cs₂ O-SiO₂ : A solution of 13.6 gm Th(NO₃)₄ ·4H₂ O, 39.4gm of AlCl₃ ·6H₂ O and 0.42 gm of Cs(acetate) in 50 ml absolute ethanolwas prepared. To this solution 37 ml of Si(EtO)₄ was added, followed by22.5 gm of urea, and 50 ml of propylene oxide. The resulting gel waswashed on a Buechner funnel with absolute ethanol until it was theconsistency of a stiff paste. This paste was then extruded through a3/16" die and the resulting extrudate first dried in a vacuum oven,followed by 14 hrs. firing in air at 1650° F.

D. CaO: To 500 ml of distilled H₂ O were added 55 gm of CaO. The mixturewas warmed slightly (to about 60° C.) and stirred, then left to standovernight. The water was decanted off in the morning and the thicksuspension remaining washed with absolute ethanol on a Buechner funnel.The resulting paste was then extruded through a 1/16" die, and theextrudate dried at 140° C., followed by firing at 700° C. for one hour.

E. MgO: This catalyst was purchased from Alfa Products, crushed and theportion passing 10 mesh, but remaining on 12 mesh screen used.

F. Li₂ O/MgO: Crushed and sized (10/12 mesh) MgO pellets (Alfa) Productswere placed in a wire bucket, and dipped in a solution of 18.5 gm LiNO₃in 50 ml warm pyridine. After dipping the pellets were dried in a vacuumoven. Dipping and drying was repeated until the weight increased by 9.4gm. This material was then fired at 1000° C. for 10 hrs., and kept in asealed jar until used.

G. Cr₂ O₃ -Al₂ O₃ -Cs₂ O: A solution of 13.06 gm CrCl₃, 43.38 gm AlCl₃and 0.42 gm of Cs(acetate) in 315 ml of absolute ethanol was prepared.To cause the CrCl₃ to dissolve a small amount (less than 3 gm of CrCl₂)was added to the above mixture. To this solution, 250 ml of H₂ O wereadded. After filtering, 115 ml of propylene oxide were added to theaqueous ethanolic solution, followed by sufficient ammonium hydroxide tocause rapid gelling. This gel was then washed with absolute ethanol on aBuechner funnel, and the resulting paste extruded through a 3/16" die.The extrudate was dried overnight in a vacuum oven and then fired in airat 1000° F. for 10 hrs.

H. ZrO₂ -Al₂ O₃ -SiO₂ : A solution of 53.61 gm ZrCl₄ and 11.84 gm AlCl₃·6H₂ O in 600 ml of warm absolute ethanol was prepared. After filteringthrough celite, the filtrate was allowed to cool to room temperature,and 75.75 ml of (EtO)₄ Si added and stirred thoroughly. To this clearsolution were then added 500 ml of H₂ O, followed by 105 ml of propyleneoxide, with constant stirring. After about 45 minutes, a gel formed. Thegel was allowed to stand overnight at room temperature, and was thenfiltered, and washed repeatedly with absolute ethanol in a largeBuechner funnel. The resulting paste was extruded through a 1/16" dieand the extrudate dried at 100° C. in a vacuum oven. The dried extrudatewas then fired at 800° C. for 12 hrs. It was then sieved to removefines, and the 10/20 mesh fraction used.

I. K₂ O/Al₂ O₃ : to 60 gm of white fused refractory alumina(Carborundum) were added a solution of 0.27 gm of K₂ CO₃ in 3 ml H₂ O.The solution was added dropwise with stirring to distribute ituniformly. The mixture was dried in an over at 150° C. for 2 hrs., thenfired in a muffle furnace at 800° C. for 17 hrs.

J. SrO/MgO: Strontium nitrate was first prepared by slowly adding 70 gmof SrCO₃ to 57 ml of concentrated nitric acid with constant stirring.This mixture was heated 3 hrs. on a hot plate until all CO₂ evolutionceased. The wet precipitate formed was collected and placed in a vacuumoven at 100° C. overnight. The resulting Sr(NO₃)₂ was a hard white drycrystalline solid. A saturated solution of Sr(NO₃)₂ in dimethylformamide was prepared and 20.4 gm of 10/12 mesh crushed MgO pellets(Alfa) dipped in the dimethylformamide solution, then dried. When 28 gmof Sr(No₃)₂ had been deposited, the coated MgO was fired at 1000° F. inair for 4 hrs.

K. BaO/Al₂ O₃ : The support for this catalyst was prepared by crushingand sieving fused white alumina refractory bubbles, obtained fromCarborundum Company. Particles in the size range 8 to 12 mesh were used.To 20 gr. of this support was added a solution of 0.6 gr Ba(NO₃)₂ in 4ml of distilled water. The addition was carried out dropwise, withcontinuous stirring of the support. After drying 3 hrs at 120° C., thecatalyst was calcined at 800° C. in air for 3 hrs.

L. ZrO₂ -SiO₂ -Al₂ O₃ : This catalyst was a low area support purchasedfrom Norton Co., their designation SZ 5245, which was crushed andsieved. Particles in the range 12-20 mesh were used.

N. ThO₂ /Al₂ O₃ : Fused white alumina refractory bubbles, obtained fromthe Carborundum Company were crushed and sieved and the fraction 8-20mesh used in preparing this catalyst. To 354.5 gr of the crushed andsieved refractory bubbles was added a solution of 43.6 gr Th(NO₃)₄ ·H₂ Oin 70.9 ml of distilled water. Small portions of the solution were addedwith continuous stirring. The wet slurry was placed in the flask of aRotovac apparatus, and ammonia vapors passed over the mixture while theflask was rotated. Thorium hydroxide was precipitated on the support bythis procedure. Even dispersion was maintained by the flask rotation.The mixture was first dried under a heat lamp in a stream of nitrogen,then calcined in air at 1000° C. for 3 hrs.

O. (La₂ O₃ -SrO)/Al₂ O₃ : Fused white alumina refractory bubbles,obtained from the Carborundum Company were crushed and sieved, and theparticles in the size range 12-20 mesh used. To 20 gr of this materialwas added a solution of 2.40 gr La(NO₃)₃ ·H₂ O and 0.6 gr Sr(NO₃)₂ in 4ml of distilled water. The solution was added dropwise with continuousstirring. The wet mixture was then dried in an oven at 200° C. for 2hrs, and finally calcined for 3 hrs in air at 1000° C.

Examples 1-11, 15, 18, 21, 24 and 25 illustrate various preferredembodiments of the invention using various metal compound-containingcatalysts and reaction conditions. All of these examples illustrate thathigh yields of higher molecular weight hydrocarbons, particularlyaromatics, are obtained when using the critical process conditions ofthe present invention.

Examples 12-14, 16-∫, 19-20 and 22-23 are not part of the presentinvention and were run for comparative purposes using various catalystsfrom different Groups of the Periodic Table. These examples whencompared to the examples falling within the scope of the presentinvention illustrate the criticality of temperatures greater than 1000°C. and space velocity greater than 3200hr⁻¹ in obtaining highconversions of methane to the desired liquid products.

Comparison of Examples 9 and 12, Table I, illustrates that for acatalyst containing predominantly a Group IVB metal compound that arelatively small change in gas hourly space velocity from 3600 to 3100hr⁻¹ resulted in a dramatic and highly detrimental increase in thetar/coke yield of 33% and that it also had the extremely undesirableeffect of decreasing the fraction of the most desired product, i.e. thearomatics, by a factor of 4.

Comparison of Example 13 with 14, Table II, illustrates that for a GroupIIA metal compound-containing catalyst that the conversion of methane isunacceptably low at a temperature of 975° C. and the production of cokeis unacceptable high at a space velocity of 3174 hr⁻¹. Examples 4-6, 11and 15 illustrate high conversions of methane to the desired productsusing various Group IIA metal compound-containing catalysts withtemperatures greater than 1000° C. and space velocities greater than3200 hr⁻¹.

Comparison of Example 16 with 18, Table II, illustrates that conversionof methane at temperatures below 1000° C. is unacceptably low with acatalyst containing a Group IVB metal compound. Comparison of Example 17and 18 illustrates the dramatic and unacceptable increase in theproduction of coke when the space velocity is below 3200 hr⁻¹. Examples8, 9, 12, and 18 illustrate high conversions of methane to the desiredproducts using Group IVB metal compound-containing catalysts withtemperatures greater than 1000° C. and space velocities greater than3200 hr⁻¹.

Comparison of Example 19 with 21 illustrates that conversion of methaneat temperatures below 1000° C. is unacceptably low with a catalystswhich is a Group IIIA metal compound. Comparison of Example 20 and 21illustrates the dramatic and unacceptable increase in the production ofcoke when the space velocity is below 3200 hr⁻¹. Examples 1 and 21illustrate high conversions of methane to the desired products usingGroup IIIA metal-containing catalysts with temperatures greater than1000° C. and space velocities greater than 3200 hr⁻¹.

Comparison of Example 22 with 24 illustrates that conversion of methaneat temperatures below 1000° C. is unacceptably low with a supportedActinide Series metal compound-containing catalyst. Comparison ofExample 23 and 24 illustrates the dramatic and unacceptable increase inthe production of coke when the space velocity is below 3200 hr⁻¹.Examples 2, 3, and 24 illustrate high conversions of methane to thedesired products using Actinide Series metal compound-containingcatalysts with temperatures greater than 1000° C. and space velocitiesgreater than 3200 hr⁻¹.

Example 25 illustrates high conversions of methane to the desiredproducts using mixtures of Group IIA and IIIA metal compound-containingcatalysts with temperatures greater than 1000° C. and space velocitiesgreater than 3200 hr⁻¹.

What is claimed is:
 1. A process for the production of higher molecular weight hydrocarbons from lower molecular hydrocarbons comprising the steps of:(a) introducing into a reaction zone a lower molecular weight hydrocarbon-containing gas and contacting said gas in said zone with a metal compound-containing catalyst having a surface area in the range 0.1 to 10 m² /gram and containing a carbide, nitride, boride or oxide of a Group I-A metal, under C₂ + hydrocarbon synthesis conditions such that at least 15 mole percent of the lower molecular weight hydrocarbons in said gas are converted to higher molecular weight hydrocarbons, said conditions including a temperature of greater than 1000° C. and a gas hourly space velocity of greater than 3200 hr⁻¹ ; (b) withdrawing from said reaction zone a higher molecular weight hydrocarbon-containing stream.
 2. The process of claim 1 wherein said temperature is in the range of 1100 to 1200° C., said space velocity is in the range of 6,000 to 36,000 hr⁻¹ and at least 20 mole percent of said lower molecular weight hydrocarbons are converted to higher molecular weight hydrocarbons.
 3. The process of claim 2 wherein said reaction zone contains a stationary or fluidized bed of a catalyst.
 4. The process of claim 3 wherein said lower molecular weight hydrocarbon is methane.
 5. The process of claim 4 wherein said temperature is in the range of 1140° to 1175° C. and said space velocity is in the range of 9,000 to 18,000 hr⁻¹.
 6. The process of claim 5 wherein 40 or more mole percent of said methane containing hydrocarbon gas is converted to higher molecular weight hydrocarbons.
 7. The process of claim 6 wherein said higher molecular weight hydrocarbon stream is rich in ethylene or aromatics or both.
 8. A process for the production of higher molecular weight hydrocarbons from methane comprising the steps of:(a) introducing into a reaction zone a methane-containing gas and contacting said gas in said zone with a catalyst having a surface area in the range 0.1 to 10 m² /gram and containing a carbide, nitride, boride or oxide of a Group I-A metal selected from lithium, potassium or cesium under C₂ + hydrocarbon synthesis conditions such that at least 20 mole percent of said methane in said gas is converted to higher molecular weight hydrocarbons, said conditions including a temperature in the range of 1100 to 1200° C. and a gas hourly space velocity of 6,000 to 36,000 hr⁻¹ ; and (b) withdrawing from said reaction zone a higher molecular weight hydrocarbon-containing stream, wherein the carbon-containing reaction products in said stream comprises greater than 90 mole percent higher molecular weight hydrocarbons.
 9. The process of claim 8 wherein at least 20 mole percent of said lower molecular weight hydrocarbons are converted to higher molecular weight hydrocarbons.
 10. The process of claim 9 wherein said reaction zone contains a stationary or fluidized bed of a catalyst.
 11. The process of claim 10 wherein said lower molecular weight hydrocarbon is methane.
 12. The process of claim 11 wherein said temperature is in the range of 1140° to 1175° C. and said space velocity is in the range of 9,000 to 18,000 hr⁻¹.
 13. The process of claim 12 wherein 40 or more mole percent of said methane containing hydrocarbon gas is converted to higher molecular weight hydrocarbons.
 14. The process of claim 13 wherein said higher molecular weight hydrocarbon stream is rich in ethylene or aromatics or both.
 15. A process for the production of higher molecular weight hydrocarbons from methane comprising the steps of:(a) introducing into a reaction zone a methane-containing gas and contacting said gas in said zone with a catalyst having a surface area in the range 0.2 to 2.0 m² /gram and containing a carbide, nitride, boride or oxide of a Group I-A metal selected form lithium, potassium or cesium under C₂ + hydrocarbon synthesis conditions such that at least 20 mole percent of said methane in said gas is converted to higher molecular weight hydrocarbons, said conditions including a temperature in the range of 1100° to 1200° C. and a gas hourly space velocity of 6,000 to 36,000 hr⁻¹ ; and (b) withdrawing from said reaction zone a higher molecular weight hydrocarbon-containing stream, wherein the carbon-containing reaction products in said stream comprises greater than 80 mole percent higher molecular weight hydrocarbons. 